Detection of circulating tumor cells in blood of pancreatic ductal adenocarcinoma patients

Aim: Previous studies suggest that circulating tumor cells (CTC) are present at very low frequencies in blood of pancreatic cancer (PC) patients. However, no technique has proven efficient for their detection, in part due to the lack of accurate tumor markers. Here, we evaluated the potential utility of two marker candidates - Mucin 16 (MUC16) and Tetraspanin 1 (TSPAN1) - identified through a detailed review of the literature. Methods: To evaluate the pattern of expression of both markers in pancreatic tumor cells vs. normal blood, we used cell lines derived from pancreatic cancer patients and blood from healthy adults. Results: Antibodies against both MUC16 and TSPAN1 showed expression in three pancreatic cancer (PC) cell lines while they were absent in blood cells. To evaluate the efficiency of isolating tumor cells from blood, PC cell lines were spiked at different frequencies in blood, sequentially stained with biotin-conjugated TSPAN1 and MUC16 antibodies and a streptavidin ferrofluids, followed by immunomagnetic enrichment. The recovery of spiked TSPAN1(+) tumor cells was high with limited contamination by leukocytes. In contrast, no PC cells were isolated when the biotin MUC16 reagent was used because the biotin-conjugated clone did not recognize PC cells. Conclusion: The combination of MUC16, TSPAN1, and epithelial cell adhesion molecule (EpCAM) antibodies will likely increase the efficiency of capturing circulating tumor cell in blood of pancreatic ductal adenocarcinoma. To further develop a protocol for isolation of circulating tumor cell in blood of PC patients, high amounts of antibodies (5-10 mg) against EpCAM, MUC16, and TSPAN1 will be needed.